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The rear axle of a truck that is frequently overloaded may experience slight collapse; consequently, many consider adding a leaf as an effective solution.
This method is occasionally employed for truck leaf springs and certain trailer leaf springs: instead of replacing the entire spring assembly, a new leaf is added to the existing set to enhance load-bearing capacity.
However, adding leafs isn’t a universal solution—this should be clearly understood before implementation.
When is the right time to add a leaf?
You can consider adding a leaf in the following cases:
The leaf spring is relatively new and shows no signs of damage.
The vehicles are often fully loaded.
You need increased strength without worrying about the steering wheel feeling “stiffer” during driving.
The add a leaf method will no longer apply in the following cases:
The broken leaf spring exhibits obvious cracks or other visible damages.
The leaf spring has been in service for an excessively long period, resulting in severe fatigue in its structure.
In this case, a direct leaf spring replacement should be performed—Safety comes first.
What exactly has adding a Leaf changed?
When adding a leaf to the existing leaf spring suspension, the primary objective is to enhance the spring’s strength.
In addition, the benefits of doing so typically include:
The load-bearing capacity of the vehicle has been improved.
The vehicle body is slightly elevated (It might be a bit higher than you expected).
The sinking amplitude decreases when the vehicle is fully loaded.
Of course, the side effects will also be more pronounced:
When idle, the vehicle becomes slightly stiffer—in other words, the driving sensation changes, requiring the driver to readjust.
How to add a leaf
First, we emphasize one key point: bolts should not be reused. Before commencing work, ensure you have prepared a jack, a support frame, new leaf spring u-bolts, and a center bolt.
- Lubrication: Spray WD40 on the bolts about one day in advance; this will make your work the next day much easier.
- Fixation: Support the unloaded truck with a jack, allowing the axles to hang freely, ensuring the leaf spring remains stable in any direction.
- Remove U-bolts: Loosen the leaf spring U-bolts and remove the pressure plate.
- Fixed spring assembly: Use a C-clamp to secure the spring assembly from both sides to prevent the leaves from separating during subsequent procedures.
- Remove the Center Bolt: Disassemble the old leaf spring center bolt and release the C-clamp; this step must be performed as slowly as possible.
- Insert the new leaf: Slide the added leaf into the predetermined position of the spring assembly, ensuring alignment; note that final tightening is not required at this stage.
- Install new Center Bolts and U-bolts: Tighten the spring assembly and install the new bolts.
- Final tightening: After the vehicle is parked, tighten all components to the specified torque.
Our engineers recommend that you have the vehicle inspected after a certain distance.
Common mistakes
Single-side installation: Maintenance, upgrades, and replacements of leaf springs are typically performed in pairs; both sides should be updated simultaneously.
Use a old U-bolt: Once again, replace it with a new one after removing the old bolt.
Leafs not fully aligned: Check this before final tightening to prevent abnormal noises or uneven stress during operation.
Overall, adding a leaf to a leaf spring is feasible and suitable for well-maintained leaf springs; the procedure is not overly complex, though attention to detail is crucial.
Safety comes first. If you’re unsure about the condition of your leaf spring, check for any signs of damage first. For leaf springs that have been in service for an extended period, we strongly recommend replacing them directly.